1. Technical Field
The present invention relates to a treadmill, and more particularly, to a tread mill with an automatic speed control function in which a speed of a rotating belt is automatically controlled according to an exercising speed and an exercising state of an exerciser.
2. Description of the Related Art
In a conventional treadmill, in order to control a speed of a rotating belt, an exerciser has to manipulate a speed control button while walking or running and has to passively follow the manually controlled speed of the rotating belt. Therefore, such a conventional treadmill does not provide a good exercising experience to an exerciser and is also difficult to realize a natural feeling that an exerciser can have while walking or running on the ground.
In order to overcome the above problems, techniques for measuring a position of an exerciser to automatically control a speed of a rotating belt have been developed. For example, Korean Patent No. 10-0398330 discloses a treadmill which measures a position of an exerciser using an ultrasonic sensor arranged below a control panel to locate an exerciser in a central region of the treadmill belt. The treadmill accelerates the rotating belt speed to move the exerciser back to the central region if the exerciser is ahead of the central region, and the treadmill decelerates the belt speed to return an exercise to the central region if the exerciser is behind the central region.
The treadmill disclosed in Korean Patent No. 10-0398330 performs acceleration or deceleration when a position of the exerciser is within a certain range from the central region, but the treadmill cannot handle various situations such as quick deceleration when an exerciser desires to abruptly stop while running at a high speed.
In addition, when a quick deceleration occurs, an overload occurs in a motor driving portion, and the motor driving portion stops driving the motor to protect itself. Thus, a conventional treadmill cannot execute a quick deceleration.
Also, a conventional treadmill performs a deceleration at a fixed slow speed, independently of a driving speed, within a range of a deceleration which does not exceed an allowable range of a motor driving portion, and performs an emergency stop operation of the motor driving portion using a natural friction force which works on a belt and a driving motor.
Also, since an abrupt deceleration during exercise can cause an exerciser to fall due to inertia and potential injury risks, a conventional treadmill has implemented a slow deceleration or a deceleration using a natural friction force.
For the foregoing reasons, an exerciser who exercises on a conventional treadmill has a different feeling from what he/she has while walking or running on the actual ground. Further, such a conventional treadmill cannot effectively implement various exercising patterns of an exerciser.
In order to improve an overall exercise experience and to cope with various exercising patterns of an exerciser, a treadmill needs to rapidly follow acceleration and deceleration of an exerciser, but a conventional treadmill cannot perform quick deceleration and thus cannot provide a satisfactory automatic speed control function.
In the treadmill disclosed in Korean Patent No. 10-0398330 which measures a position of an exerciser by an ultrasonic sensor in order to control a speed of a belt to locate an exerciser in a central region, a measured value of an exerciser's position received from an ultrasonic sensor may contain erroneous values. Therefore, it is difficult to implement an automatic speed control function using only a technique for measuring an exerciser's position by an ultrasonic sensor in a treadmill.
In addition, measured values received from an ultrasonic sensor can be distorted due to various ambient noise, and undesired measured values, for example, a position value of an arm or a leg, may be obtained while an exerciser walks or runs. Such signal distortion and undesired measured values make it difficult for a treadmill to automatically control a speed of a belt.
Korean Patent Publication Nos. 10-2007-0015687, 10-2007-0081476, 10-2007-0082277, and 10-2007-0082929 disclose techniques and mechanisms in which load sensors are arranged below front and rear portions of a belt, measured values obtained by load sensors are used to calculate an exerciser's position, and a speed of a rotating belt is controlled based on a difference between a calculated exerciser's position and a reference position.
However, the above-described techniques using load sensors have a problem in that a cycle of a load that is applied to a load sensor depends on a speed of an exerciser, and a cycle of a load of when an exerciser runs at a highest speed is 2 or 3 times per second. This makes it very difficult to smoothly control the belt speed.
Also, a position of an exerciser's foot continuously varies due to a movement of the belt even at a moment that an exerciser's foot pushes the belt, and the frequency with which the exerciser's feet make contact with the belt when an exerciser walks on the belt is not equal to that when an exerciser runs on the belt. Thus, it is difficult to accurately calculate a position of an upper body of an exerciser or the center of gravity.
In addition, the above-mentioned Korean Patent Publications have not mentioned a control method for coping with various exercising patterns of an exerciser, such as quick acceleration or quick deceleration, and so it is difficult to automatically control the belt speed only using a difference between an exerciser's position and a reference position in a manner that provides satisfactory automatic speed control.